Improvement in castability of Al containing resulphurised free machining steel

Abstract

During the continuous casting (CC) of Al containing resulphurised steel, the submerged entry nozzle is often clogged by high melting point inclusions such as MgO.Al₂O₃ spinel and CaS. Casting extended for only one to two heats before optimisation. The main objective of the present study is to improve the castability of this steel. A suitable refining slag composition was sought and designed thermodynamically, and a soft blowing system was improved for reducing the dynamics of steel–slag desulphurisation. An optimisation plant trial was conducted on a sequence with four heats. By adopting the optimised refining slag and improved soft stirring operation, the steel castability was improved and the number of CC heats of a single tundish was increased from 1–2 to more than 4.

Keywords:

• Free machining steel
• Refining slag
• Thermodynamics
• Castability
• Inclusions